/**
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.hama.util;

import java.io.IOException;
import java.io.InputStream;
import java.net.Socket;
import java.net.SocketTimeoutException;
import java.nio.ByteBuffer;
import java.nio.channels.FileChannel;
import java.nio.channels.ReadableByteChannel;
import java.nio.channels.SelectableChannel;
import java.nio.channels.SelectionKey;

/**
 * This implements an input stream that can have a timeout while reading. This
 * sets non-blocking flag on the socket channel. So after create this object,
 * read() on {@link Socket#getInputStream()} and write() on
 * {@link Socket#getOutputStream()} for the associated socket will throw
 * IllegalBlockingModeException. Please use {@link SocketOutputStream} for
 * writing.
 */
public class SocketInputStream extends InputStream implements
    ReadableByteChannel {

  private Reader reader;

  private static class Reader extends SocketIOWithTimeout {
    ReadableByteChannel channel;

    Reader(ReadableByteChannel channel, long timeout) throws IOException {
      super((SelectableChannel) channel, timeout);
      this.channel = channel;
    }

    int performIO(ByteBuffer buf) throws IOException {
      return channel.read(buf);
    }
  }

  /**
   * Create a new input stream with the given timeout. If the timeout is zero,
   * it will be treated as infinite timeout. The socket's channel will be
   * configured to be non-blocking.
   * 
   * @param channel Channel for reading, should also be a
   *          {@link SelectableChannel}. The channel will be configured to be
   *          non-blocking.
   * @param timeout timeout in milliseconds. must not be negative.
   * @throws IOException
   */
  public SocketInputStream(ReadableByteChannel channel, long timeout)
      throws IOException {
    SocketIOWithTimeout.checkChannelValidity(channel);
    reader = new Reader(channel, timeout);
  }

  /**
   * Same as SocketInputStream(socket.getChannel(), timeout): <br>
   * <br>
   * 
   * Create a new input stream with the given timeout. If the timeout is zero,
   * it will be treated as infinite timeout. The socket's channel will be
   * configured to be non-blocking.
   * 
   * @see SocketInputStream#SocketInputStream(ReadableByteChannel, long)
   * 
   * @param socket should have a channel associated with it.
   * @param timeout timeout timeout in milliseconds. must not be negative.
   * @throws IOException
   */
  public SocketInputStream(Socket socket, long timeout) throws IOException {
    this(socket.getChannel(), timeout);
  }

  /**
   * Same as SocketInputStream(socket.getChannel(), socket.getSoTimeout()) :<br>
   * <br>
   * 
   * Create a new input stream with the given timeout. If the timeout is zero,
   * it will be treated as infinite timeout. The socket's channel will be
   * configured to be non-blocking.
   * 
   * @see SocketInputStream#SocketInputStream(ReadableByteChannel, long)
   * 
   * @param socket should have a channel associated with it.
   * @throws IOException
   */
  public SocketInputStream(Socket socket) throws IOException {
    this(socket.getChannel(), socket.getSoTimeout());
  }

  @Override
  public int read() throws IOException {
    /*
     * Allocation can be removed if required. probably no need to optimize or
     * encourage single byte read.
     */
    byte[] buf = new byte[1];
    int ret = read(buf, 0, 1);
    if (ret > 0) {
      return (byte) buf[0];
    }
    if (ret != -1) {
      // unexpected
      throw new IOException("Could not read from stream");
    }
    return ret;
  }

  public int read(byte[] b, int off, int len) throws IOException {
    return read(ByteBuffer.wrap(b, off, len));
  }

  public synchronized void close() throws IOException {
    /*
     * close the channel since Socket.getInputStream().close() closes the
     * socket.
     */
    reader.channel.close();
    reader.close();
  }

  /**
   * Returns underlying channel used by inputstream. This is useful in certain
   * cases like channel for
   * {@link FileChannel#transferFrom(ReadableByteChannel, long, long)}.
   */
  public ReadableByteChannel getChannel() {
    return reader.channel;
  }

  // ReadableByteChannel interface

  public boolean isOpen() {
    return reader.isOpen();
  }

  public int read(ByteBuffer dst) throws IOException {
    return reader.doIO(dst, SelectionKey.OP_READ);
  }

  /**
   * waits for the underlying channel to be ready for reading. The timeout
   * specified for this stream applies to this wait.
   * 
   * @throws SocketTimeoutException if select on the channel times out.
   * @throws IOException if any other I/O error occurs.
   */
  public void waitForReadable() throws IOException {
    reader.waitForIO(SelectionKey.OP_READ);
  }
}
